Hermetically sealed container for large-sized precision sheet (semi-) product

ABSTRACT

A relatively light resinous hermetically sealed container for a large-sized precision sheet (semi-)product, such as a photomask, is provided so as to accommodate, support and transport the precision sheet (semi-)product safely and in an airtight manner. The hermetically sealed container includes a main body and a lid member respectively having peripheral flange portions abutted to each other so as to accommodate a precision sheet (semi-)product therein. Each of the main body and the lid member is formed as a vacuum or air-pressure formed thermoplastic resin sheet equipped with a reinforcing rib.

FIELD OF THE INVENTION AND RELATED ART

The present invention relates to a hermetically sealed container suitably used for transportation of a precision sheet (semi-)product, i.e., a precision sheet product or a semi-product thereof before completion of the product such as a (glass) substrate thereof, inclusive of a photomask (including a reticle) or a pelicle as a protective film for such a photomask, a semiconductor wafer-related product, various display products inclusive of a liquid crystal display (LCD), etc., particularly a precision sheet (semi-) product of a large size which is intended herein to mean at least 500 mm for at least one side thereof.

A precision sheet (semi-)product as mentioned above is generally mechanically fragile in many cases, and a precision part or member formed thereon is further fragile in many cases. Moreover, in view of its properties in relation to its use, such a precision sheet (semi-)product extremely hates dirt, particularly adherent dirt of 0.3 μm or smaller, so that particular attention must be paid to hermetic sealability of a container therefor. Especially, such a sheet (semi-)product is frequently exported overseas from Japan by airplane, and minute dirt is liable to be introduced into the container due to a pressure difference between the inner space (particularly, a cargo space) of the airplane and the atmospheric pressure. Further, as the attachment of minute dirt should be avoided, the formation of a container main body with a foam resin (e.g., Japanese Patent Laid-Open Application (JP-A) 2001-31165) or the disposition of a foam resin cushioning material in a container as frequently exercised for general-purpose glass products since such a foam resin is liable to generate minute dirt due to abrasion. Further, such a precision sheet (semi-)product, particularly a display product or a photomask therefor, is inevitably enlarged in size (area) for complying with the demand for a large size and large area display, and further for allowing the exposure at one time of plural objective products, such as display products, with respect to the photomask product. Corresponding thereto, some new problems have occurred. That is, accompanying the size enlargement, the weight of a precision sheet (semi-)product per se as the content material is increased to 5-10 kg, and for supporting the weight while obviating the application of a stress to the precision sheet (semi-)product due to deformation of a container, the container is also required to have a substantial strength. However, if the container is composed of a metal material according to a conventional manner, the weight of the container is increased to 40 kg or more and the total weight thereof together with the content product is increased to 50 kg or more, so that the transportation thereof by human power becomes extremely difficult also due to the increase in outer contour size thereof. Further, the accommodation of a precision sheet (semi-)product in a container has to be performed by supporting the (semi-)product so as to prevent at least one face thereof (on which precision members are formed) from contacting another member in the container.

SUMMARY OF THE INVENTION

Accordingly, a principal object of the present invention is to provide a hermetically sealed container of a relatively light weight capable of safely accommodating and supporting a large-sized precision sheet (semi-)product, such as a photomask, therein without exerting inappropriate stress to the (semi-)product.

According to our study for accomplishing the object, it has been found very effective to use a hermetically sealed container having a two-division structure of a main body and a lid member each of which is a vacuum or air-pressure formed product of a thermoplastic resin sheet equipped with appropriate reinforcing means. More specifically, according to the present invention, there is provided a hermetically sealed container for a large-sized precision sheet (semi-)product, comprising a main body and a lid member respectively having peripheral flange portions abutted to each other so as to accommodate a precision sheet (semi-)product therein, wherein each of the main body and the lid member comprises a vacuum or air-pressure formed thermoplastic resin sheet equipped with a reinforcing rib.

The main body and the lid member constituting the hermetically sealed container for a precision sheet (semi-)product according to the present invention are respectively a vacuum or air-pressure formed product of a thermoplastic resin sheet provided in a uniform thickness unlike an injection-molded product which has an uneven thickness and is particularly liable to have a locally thick portion, so that each of the main body and the lid member exhibits a uniform strength regardless of its entirely light weight and is prevented from warp or deflection in cooperation of an integrally formed reinforcing rib regardless of its large area. The main body and the lid member respectively have the peripheral flange portions abutted to each other, thereby improving the hermetic sealing performance of the container.

BRIEF DESCRIPTINO OF THE DRAWINGS

FIG. 1 is a plan view of a main body according to an embodiment of horizontal-type container according to the invention.

FIG. 2 is a sectional view taken along an A-A line in FIG. 1.

FIG. 3 is a partial sectional view in the neighborhood of holding members of the container shown in FIG. 1.

FIG. 4 is partial sectional view showing a gap (or play) between a holding member and an edge of a (semi-)product sheet.

FIG. 5 is a perspective view showing a combination of a main body and a lid member of a vertical-type container according to one embodiment of the invention.

FIGS. 6A and 6B are a top plan view and a side view, respectively, of a main body of the container shown in FIG. 5.

FIG. 7A is a schematic front view for illustrating a structure for holding a (semi-) product sheet in the container of FIG. 5, and FIGS. 7B and 7C are sectional views taken along a B-B line and a C-C line, respectively, in FIG. 7A.

FIG. 8 is a perspective view showing a combination of a main body and a lid member of an embodiment of vertical-type container for accommodating plural (semi-) product sheets according to the invention.

FIG. 9A is a perspective view showing a taken-out state of a (semi-)product sheet-carrier in the container of FIG. 8, and FIGS. 9B and 9C are enlarged views of a part B and a part C, respectively, in FIG. 9A.

DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinbelow, the present invention will be described more specifically with respect to preferred embodiments thereof while referring to the accompanying drawings.

(Horizontal-Type Structure)

FIG. 1 is a plan view of a main body 10 of a hermetically sealed container for a large-sized precision sheet (semi-)product of a horizontal type (i.e., a type of structure wherein a precision sheet (semi-)product is accommodated in a position generally parallel to an abutting plane between peripheral flange portions of a main body and a lid member); FIG. 2 is a sectional view taken along an A-A line as viewed in the direction of arrows in FIG. 1, and FIG. 3 is a partial sectional view in the neighborhood of a periphery showing a combined state of the main body 10 and a lid member 20 thereof.

Referring to FIGS. 1 and 2, the container main body 10 of this embodiment is a main body of a horizontal-type container for a photomask for a liquid crystal display (LCD) formed on a synthetic quartz-made substrate having a shape of roughly horizontal rectangle (more specifically, having sizes of L (longitude): ca. 700 mm×T (transverse) ca. 800 mm) (hereinafter sometimes referred to as a “(semi-)product sheet”, and the container has planar contour sizes of ca. 880 mm×ca. 930 mm×ca. 50 mm in depth. The container main body is generally made of a vacuum or air-pressure formed product of a thermoplastic resin sheet having a thickness of ca. 5 mm and is provided at its bottom with 4 ca. 580 mm-long reinforcing ribs 2 having an arcuate section of ca. 30 mm in curvature radius and ca. 10 mm in height and arranged in a form of cross bars.

Along 4 sides of a peripheral portion of a vacuum or air-pressure formed sheet 1 forming the main body 10 (hereinafter sometimes simply referred to as a “main body 1”), a flange portion 3 of ca. 100 mm in, width is formed so as to surround a zone 4 for accommodating a precision sheet (semi-) product. The flange portion 3 is formed at a position higher by ca. 50 mm than the bottom in the accommodation zone 4. At 4 sides in proximity to outer periphery of the accommodation zone 4, 3 pieces each of (semi-)product sheet-holding members 5 are formed. The holding members 5 each comprise a sheet-supporting portion 5 a having a taper of downwardly ca. 5 degs. toward the center and a sheet-abutting side wall portion 5 b having a height slightly smaller than the thickness of the (semi-)product sheet A (FIG. 3). The holding members 5 are disposed as inserts in a mold in advance of the vacuum or air-pressure forming of the main body 1, and are integrally caught and fixedly held in the formed resin sheet at the time of the vacuum or air-pressure forming. Particularly, the portion of the formed resin sheet fixedly holding the holding members 5 forms aprons 6 at an intermediate height of ca. 30-40 mm from the bottom so as to support the weight of the (semi-)product sheet A applied to the holding members 5. On the peripheral flange portion 3 and along its whole peripheral length, a groove 7 is formed for receiving an elastic O-ring for improving the hermetic sealing performance of the container. Further, at 4 corners of the peripheral flange portion 3, projections 8 a and recesses 8 b are formed for positional alignment with a lid member disposed opposite to the main body 10 so as to allow the positional alignment by fitting with alignment recesses 8 b and projection 8 a formed at the corresponding positions of the lid member.

At outer edges of the peripheral flange portion 3, generally downward flaps 3 a are formed to exhibit a reinforcing function, and at parts thereof (2 parts each for each side in this embodiment), cutouts 3 b are formed. The peripheral flange portion 3 is further provided with several set screw holes 3 c.

A lid member 20 (only a portion of which is shown in FIG. 3) used in combination with the main body 10 has a structure roughly symmetrical with the main body 10 and is different from the main body, in this embodiment, only in that the O-ring groove 7 is not provided and it has (semi-)product sheet-holding members 15 having a taper portion 15 a longer than the taper portion 5 a of the (semi-)product sheet-holding members 5 of the main body while omitting the sheet-abutting side wall portions.

A state of use of the container for a precision sheet (semi-)product comprising the main body 10 and the lid member 20 is shown in FIG. 3. A (semi-)product sheet A is held at its edge by being sandwiched between the holding members 5 and 15, and the hermetic sealing of the container is secured by sandwiching an O-ring 9 under pressure with the flanges 3 and 13. The pressing force exerted between the holding members 5 and 15 and between the flanges 3 and 13 sandwiching the O-ring 9 is provided by disposing clamp locks between the flanges 3 and 13, by disposing ratchet buckle locks at the peripheral cutouts, or by screw setting by using the set screw holes 3 c.

Incidentally, the edge of the (semi-)product sheet A need not be abutted against the side wall 5 b of the holding member 5 as shown in FIG. 3 but may be held while leaving some gap from the side wall 5 b as shown in FIG. 4. Particularly, as the distance between the side walls 5 b of an opposing pair of the holding members 5 disposed at the opposing sides of the main body is set to be somewhat longer than the width of the (semi-)product sheet A, it is a usual state that some gap (or play) as shown in FIG. 4 occurs on at least one of the opposing sides. Further, in this embodiment, the height of the sheet-abutting side wall of the holding member 5 on the main body side is set to be slightly lower than the thickness of the (semi-)product sheet A, and the length of the taper portion 15 a of the holding member 15 on the lid member side is set to be larger than that of the taper portion 5 a of the holding member 5 on the main body side. As a result thereof, even if some lateral deviation occurs at the time of fixing the holding member 15, it is possible to prevent a (left) horizontal part of the lower face of the holding member 15 a from contacting to damage the upper face of the (semi-)product sheet A as shown in FIG. 4. If the difference in length of the taper portion is set to be larger, the safety of avoiding a trouble caused by the fixing positional deviation is increased, but too large a difference is liable to result in insufficiency of holding (tightening) of the (semi-)product sheet A. Incidentally, it is of course possible to dispose a holding member having a sheet-abutting side wall on the lid member side and dispose a holding member having a longer taper portion on the main body side.

(Material)

Explanation of materials of the respective parts is supplemented. The vacuum or air-pressure product 1 constituting the portions other than the (semi-)product sheet-holding members 5 of the main body 10 can comprise any thermoplastic resin but may preferably comprise an antistatic resin so as to obviate electrostatic attraction of minute dirt to a (semi-)product sheet contained therein. Known examples of such an antistatic resin having permanent antistaticity may include one having a composition of: (a) a hydrophilic polymer: 3-100 wt. parts, (b) a thermoplastic resin: 0-97 wt. parts (giving a total of 100 wt. parts together with (a)), and (c) a polyvalent metal compound: 0.001-0.5 wt. part (WO-A 03/033590), which composition is suitably used in the present invention. However, in case where an extreme level of optical property (prevention of haze) is not required, the addition of (c) a polyvalent metal compound is not required. It is particularly preferred to use (a) a hydrophilic polymer comprising a graft copolymer including a rubber trunk polymer having an alkylene oxide group, and an anionic surfactant (JP-A 59-2462), and further a rigid thermoplastic resin, such as a polyacrylonitrile resin, a polystyrene resin or a polymethyl methacrylate resin, in order to provide a rigidity so as not to readily apply a warp stress to the (semi-)product sheet. Incidentally, in a specific example of the above-described embodiment, a vacuum formed product 1 of a 5 mm-thick antistatic resin sheet comprising 10 wt. % of the above-mentioned hydrophilic polymer and 90 wt. % of a polyacrylonitrile resin (“BAREX 210”, made by BP Amoco) and exhibiting a flexural rigidity of 2 GPa., was used.

The (semi-)product sheet-holding members 5 can also comprise an antistatic resin as mentioned above but, even in this case, it is inappropriate to form the holding members 5 as integral portions (i.e., having a substantially equal thickness) of the vacuum or air-pressure formed product since it is difficult to support a concentrated stress including the weight of the (semi-)product sheet by such a structure. Accordingly, in such a case, it is preferred to form the holding members 5 as separate pieces of antistatic resin and places the holding members as inserts in a mold to effect vacuum or air-pressure forming of an antistatic resin sheet, thereby having the formed resin sheet to integrally capture and securely hold the holding members 5 therein. If the holding members are fixedly held with the main body or lid member by using set screws instead of the insert forming, the resultant hermetic sealing is liable to become incomplete. Further, if the holding members are fixed with an adhesive, the (semi-)product sheet A is liable to be soiled with the adhesive. Accordingly, insert forming as described above is preferred. As there is some gap (play) between the side wall 5 b of a holding member 5 and the edge of the (semi-)product sheet A, some slide of the holding member 5, particularly a supporting part 5 a thereof, with the edge of the (semi-)product sheet A can occur. Accordingly, it is further preferred to use a relatively soft resin having a slidability or a self lubricating property, inclusive of a fluorine-containing resin such as polytetrafluoroethylene, an olefin resin such as polyethylene, or polyacetal resin, rather than the resin constituting the vacuum or air-pressure formed product 1. In a specific example, holding members 5 made of polytetrafluoroethylene and having a roughly character L-shaped section, were used.

The O-ring 9 (FIG. 3) may preferably comprise an elastomeric resin, such as fluorine-containing rubber or silicone rubber, and particularly preferably such an elastomeric resin imparted with antistaticity. The O-ring is not restricted to a solid one (of e.g., 8 mm in diameter) as shown but may also preferably comprise a hollow one (of e.g., 8 mm in outer diameter and 4-6 mm in inner diameter) so as to increase the deformation stroke.

(Modifications)

In the above, a horizontal-type container for an LCD-photomask has been described as a preferred embodiment. However, the above-described embodiment of container can be modified in various manners. Some examples of such modifications are described below.

For example, the holding members 5 are used in a number of 3 for each side, and totally 12, in the above embodiment but the number can be increased or decreased as desired, of course. However, it is preferred to use at least two holding members for each side, and thus totally at least 8 holding members. Further, in the above embodiment, the projections 8 a and the recesses 8 b are disposed in a number of 2 each and totally 4 at positions proximate to the 4 corners on the peripheral flange portion of the main body and also on the peripheral flange portion of the lid member for positional alignment between the main body and the lid member but these alignment means can also be disposed at intermediate positions on the 4 sides and can be increased or decreased as desired (provided that at least two of such alignment members are preferably provided to each of the main body and the lid member). It is preferred that the main body and the lid member are equally provided with equal numbers of projections 8 a and recesses 8 b so as to impart common structures, as far as possible, to the molds for vacuum or air-pressure forming of the main body and the lid member, but it is structurally possible that one of the main body and the lid member is provided with projections 8 a and the other is provided with recesses 8 b. Similar modification is possible for the O-ring groove 7. More specifically, if the O-ring groove 7 is made shallower and a symmetrical O-ring groove is also provided to the peripheral flange portion of the lid member, the portions formed by vacuum or air-pressure forming (i.e., regardless of the shape of and except for the holding members disposed as inserts in the forming) can be made utterly symmetrical in shape, so that it becomes even possible to use a common mold for the formation of the main body and the lid member.

The downward flaps 3 a of the peripheral flange portion 3 are preferred for the reinforcement purpose but are not essential. It is also possible to omit the cutouts 3 b and the set screw holes 3 c.

The sectional shapes of the reinforcing ribs 2 and the alignment projections 8 a and recesses can be rectangular instead of the hemi-circle or hemi-spherical one.

(Vertical-Type Structure)

The hermetically sealed container for a precision sheet (semi-)product of the present invention can also be composed as a vertical-type container (i.e., a type of structure wherein a precision sheet (semi-)product is accommodated in a position generally vertical to the abutting faces of the peripheral flange portions of the main body and the lid member). As an embodiment of such a vertical-type container, a container of a glass substrate for production of various displays is described with reference to FIG. 5 (a perspective view showing a combination of a main body and a lid member); FIGS. 6A and 6B (6A: a top plan view and 6B: a side view, of the container main body), and FIGS. 7A-7C (7A: a front view, 7B and 7C: side views, for illustrating a manner of holding a (semi-)product sheet in the container).

More specifically, as shown in FIG. 5, the vertical container comprises a main body 30 having a mouth circumference of ca. 2200 mm and a height of ca. 350 mm, and a lid member 40 having a height of ca. 180 mm, which are composed as vacuum or air-pressure formed products 21 and 31, respectively, of a ca. 5 mm-thick antistatic resin sheet (comprising 10 wt. % of a hydrophilic polymer and 90 wt. % of a polyacrylonitrile-based resin) and are provided with side wall-reinforcing ribs 22 and 32, respectively. The main body and the lid member have ca. 30 mm-wide peripheral flange portions 23 and 33, which are abutted to each other, and the peripheral flange portion 23 of the main body 30 is provided with an O-ring-receiving groove 27. Inside the main body, a pair of holding members 25 provided at centers thereof with grooves 25 a for inserting and holding a sheet are inserted along guide groove members 26 so that their upper ends extend upwards beyond the peripheral flange portion 23. As shown in FIG. 6A, at the bottom of the main body, reinforcing ribs 22 a are formed, and holding members 26 a each having a groove 26 aa for holding a lower end of the holding member 25 are disposed. At the time of using the container, a (semi-)product sheet A2 is inserted along the sheet-insertion and holding grooves 25 a of the holding members 25, which in turn are inserted along the guide groove members 26 and held at their lower ends with the holding grooves 26 aa of the holding members 26 a, and the (semi-)product sheet A2 is held at its lower end with a sheet's lower end-holding member 25 b provided with a sheet-holding groove 25 bb disposed at the bottom of the main body. The (semi-)product sheet A2 is further held at its upper end with a holding member 35 provided with a holding groove 35 b and disposed at the bottom of the lid member 40, thereby being accommodated in the container comprising the main body 30 and the lid member 40. Prior to the abutting of the peripheral flange portions of the main body 30 and the lid member 40, an O-ring (not shown) is disposed in the receiving groove 27, and the hermetic sealing of the container is ensured by an abutting pressure exerted by clamp locks or ratchet buckle locks disposed between the peripheral flange portions 23 and 33 and applied to the peripheral flange portions.

The materials of the vacuum or air-pressure formed products 21 and 31, and the holding members 25, 25 b, 26 a, 35, etc., are similar to those of the vacuum or air-pressure formed product 1 and the holding members 5 described with reference to FIGS. 1 to 4.

(Further Modifications)

The above description has been principally directed to embodiments of containers adapted to accommodation of one (semi-)product sheet. However, the hermetically sealed container of the present invention is also applicable to accommodation of plural (semi-)product sheets. FIG. 8 is a schematic perspective view showing an embodiment of such a hermetically sealed container for accommodating plural precision sheet (semi-)products in a state where the lid member is taken off upwards. Referring to FIG. 8, the vertical-type container comprises a main body 50 and a lid member 60 which are formed as vacuum or air-pressure formed resin products 51 and 61, respectively, equipped with nozzles 52 and 62 for replacement of gas inside the container. Inside the main body 50 is disposed a carrier 53 for receiving and carrying, e.g., 10 (semi-)product sheets. FIG. 9A is an enlarged view of such a (semi-)product sheet-carrier 53 in its state of being taken out of the main body, and FIGS. 9B and 9C are enlarged views of parts B and C, respectively, in FIG. 9A. More specifically, the (semi-)product sheet-carrier 53 comprises a pair of resin sheets 531 each provided with guide grooves 532 for receiving and supporting, e.g., 10 (semi-)product sheets, vertically in parallel and a grip 533 for moving the carrier, and metal frames 534 for fixedly supporting the resin sheets 531 and securing a spacing between them. As a result, e.g., 10 (semi-)product sheets are allowed to be inserted along the guide grooves 532 (FIG. 9B) and supported at their lower ends with bottoms 532 c of the grooves 532 (FIG. 9C), and the carrier 53 in the thus-loaded state can be moved into and out of the main body 50. The lower ends and the upper ends of the plural (semi-)product sheets are protected with silicone rubber, fluorine-containing resin, etc., so as to alleviate the shock exerted thereto at the time of transportation thereof. Further, at the inside bottom of the main body 50, grooves may be formed so as to receive the lower ends of the resin sheets 531, thereby accommodating the carrier 53 while preventing a lateral vibration, etc., of the carrier. If desired, the lid member 60 may also be provided with grooves for receiving the upper ends 531 b of the resin sheets 531 so as to improve the fixation of the carrier. The nozzles 52 and 62 provided to the main body 50 and the lid member 60, respectively, for replacement of gas inside the container, are suitable, e.g., for replacing the inside atmosphere of a container for a (semi-)product sheet, such as an EL (electro-luminescence)-related sheet product, which should be free from moisture in addition to the attachment of dirt. Such nozzles can also be attached, if desired, to a horizontal-type container as described with reference to FIGS. 1 to 4.

As described above, according to the present invention, there is provided a relatively light resinous container capable of accommodating, supporting and transporting a large-sized precision sheet (semi-)product, such as a photomask, safely and in an airtight manner without exerting an inappropriate stress thereto. 

1. A hermetically sealed container for a large-sized precision sheet (semi-)product, comprising a main body and a lid member respectively having peripheral flange portions abutted to each other so as to accommodate a precision sheet (semi-)product therein, wherein each of the main body and the lid member comprises a vacuum or air-pressure formed thermoplastic resin sheet equipped with a reinforcing rib.
 2. A container according to claim 1, wherein each of the thermoplastic resin sheets forming the main body and the lid member comprises an antistatic resin.
 3. A container according to claim 1, wherein at least one of the peripheral flange portions of the main body and the lid member is provided with a groove for receiving an O-ring for hermetic sealing.
 4. A container according to claim 1, wherein a plurality of holding members for holding the precision sheet (semi-)product are disposed at plural positions adjacent to the peripheral flange portions of the main body and the lid member, respectively.
 5. A container according to claim 4, wherein each holding member on one of the main body and the lid member comprises a tapered portion and an abutting side wall having a height smaller than the thickness of the precision sheet (semi-) product, and each holding member on the other of the main body and the lid member has a tapered portion longer than the tapered portion of the holding member on said one of the main body and the lid member.
 6. A container according to claim 4, wherein the holding members are integrally captured with the vacuum or air-pressure formed thermoplastic resin sheet and held therewith.
 7. A container according to claim 6, wherein the holding members comprise a thermoplastic resin which is softer and richer in slidability than the thermoplastic resin sheet.
 8. A container according to claim 4, wherein the vacuum or air-pressure formed thermoplastic resin sheet is provided with aprons adjacent to the holding members for providing a reinforced strength for supporting the weight of the precision sheet (semi-)product. 